|Publication number||US4103594 A|
|Application number||US 05/480,191|
|Publication date||Aug 1, 1978|
|Filing date||Jun 17, 1974|
|Priority date||Jun 26, 1973|
|Also published as||DE2429977A1, DE2429977C2|
|Publication number||05480191, 480191, US 4103594 A, US 4103594A, US-A-4103594, US4103594 A, US4103594A|
|Original Assignee||Robert Geffroy|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (12), Referenced by (18), Classifications (16)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
This invention relates to piston and oil scraper ring assemblies of the type employed in engines, compressors and other machines, and more particularly to an improved piston and scraper ring assembly having means for providing more efficient and complete return of oil from a cylinder wall to the oil sump.
2. Description of the Prior Art
The pistons movable in cylinders in internal combustion engines, compressors and other machines (hereinafter referred to generally as engines) are generally equipped with a scraper ring mounted in a groove in the piston and intended primarily to restrict the passage of oil between the crank case and the working chamber of the piston. During every piston stroke, the ring scrapes the oil off the walls of the cylinder and recycles it to the crankcase by way of the gap between those mutually adjoining ring and groove surfaces which are leading during that stroke of the piston, and then by way of orifices, generally in the bottom of the groove, leading to the crank case via the interior of the piston.
During each stroke this oil recycling circuit is open due to the pressure of the piston on the ring until the time during the second half of the stroke when inertia forces arising from deceleration of the piston throw the ring on to that side of its groove which is leading at the time. This interrupts the oil recovery circuit for the remainder of that stroke, and at each dead center the ring accumulates, against its leading side and against the cylinder, a band or film of scraped oil which escapes from the recycling circuit. The band of oil deposited at the top dead center has a considerable effect on the oil consumption of an engine, and the present invention is concerned with recovering at least some of this band of oil at the top dead center position.
According to this invention there is provided a piston having at least one peripheral groove containing a scraper ring, and having a recess in the piston in a position adjoining that scraper lip of the ring which is nearer the crown of the piston, the recess being such as to constitute a reservoir without outlet for a liquid subjected to a force attracting it towards the crown of the piston, to cooperate with the said scraper lip on the ring and with an oil recovery lip formed at the circumferential face of the piston and bounding one side of the recess, which oil recovery lip is disclosed close to the said scraper lip, and to communicate, by way of a passage between those adjacent sides of the ring and groove which are closer to the crown of the piston, with an outlet from the groove.
These features of the invention will be apparent from the following description of two embodiments of the invention, given by way of example and illustrated in the accompanying drawings in which:
FIG. 1 represents a fragmentary axial section through a first embodiment; and
FIG. 2 is a corresponding view of another embodiment.
FIG. 1 shows a piston 101 movable in a cylinder 102 and containing a scraper-ring groove 103, which communicates with the crank case by way of holes 105 and the hollow interior 104 of the piston 101. The scraper ring 106 may be conventional, but preferably has a sharp-edged scraper lip 107 at its upper side or the side nearer the piston crown. At the radial outer edge portion of the upper side 108 of groove 103, the piston has a recess in the form of an annular channel 109 with a downwardly directed circumferential lip 110, which preferably has a sharp edge close to the scraper lip 107 and the wall of cylinder 102. This channel 109 is joined to the upper side of the groove by a rounded portion 111. The recess 109 preferably has its deepest portion 112 furthest from the cylinder.
Between its groove 103 and the crankcase, the piston has a second peripheral recess 113 connected to the piston skirt by a transition portion or profile 114 which promotes dynamic entraining of the oil from the recess 113 into the gap 115 between the piston and cylinder walls during strokes in the direction of top dead center. The recess 113 is connected to the crankcase side of the groove by a rounded portion 116.
FIG. 2 illustrates, in a manner similar to the first embodiment, a piston 201 movable in a cylinder 202 and containing a groove 203 for a scraper ring 206. The piston 201 is provided with a recess in the form of an annular channel 209 similar to the channel 109, and a circumferential lip 210 similar to the circumferential lip 110.
This assembly has various additional features, which may be used separately or together, as follows:
The scraper ring 206 has, at its side remote from the crankcase, a lower lip 220 with a frusto-conical sloping surface 221 which guides the oil scraped during the upward strokes of the piston towards the piston axis and away from the piston crown into a zone 222 open to the recess 209, where the oil is not in contact with the cylinder;
The inner diameter of the frusto-conical surface 221 is smaller than the diameter of the oil recovery lip 210 on the piston;
The circumferential lip 210 is close to the scraper lip 207 and cylinder 202;
The adjacent portions 208 of the upper sides of the groove and ring are parallel and frusto-conically inclined towards the piston axis in a direction away from the crown of the piston;
Radiused portions 211, 223, 224 and 216 are provided on the piston 201 and ring 206 to promote the passage of fluid along the drainage circuit formed between the recess 209 and the gap 215 between cylinder and piston skirt;
A recess 213 and a profile 214 connecting it to the gap 215 between cylinder and piston are similar to features 113 to 115 in FIG. 1; and
The groove 203 does not have orifices connecting it to the interior of the piston 204, but a permanent connection between the bottom of the groove 203 and the crankcase is ensured, in this embodiment, by radial slots or orifices 225, which are shown in the ring 206, but which could equally well be in the lower side of the piston groove.
The embodiment shown in FIG. 1 operates as follows.
During the first half of each rising stroke of the piston (i.e., the stroke from bottom dead center to top dead center) the scraper ring 106 is pressed against the crankcase side of its groove, due to friction of the ring against the cylinder and due to inertia. From the half-way point the inertia is reversed, and when it is great enough to overcome the friction it presses the scraper ring 106 against the upper surface 108 of its groove. During the first part of this stroke, therefore, the adjacent sides 117 of the groove and ring are in contact, and there is clearance between the adjacent portions 108 of the groove and ring. The oil scraped off the cylinder 102 by the lip 107 on the ring 106 passes through the clearance at 108 and returns to the crankcase as indicated by an arrow f1.
During the second part of the piston stroke this flow route is closed due to contact between the surfaces 108 as shown in FIG. 1, and until the top dead center is reached the upper lip of the scraper ring 107 scrapes the oil along the cylinder, so than an annular pool or band of oil forms in contact with the upper side of the scraper ring and with the cylinder. During the next stroke of the piston, which is downward from top dead center to bottom dead center, the oil band so deposited is at least partly recovered by the lip 110 on the piston and is urged by its own inertia into the deepest portion 112 of the circular recess 109. This band of oil, therefore, does not remain on the cylinder and is not, as heretofore, collected by the compression ring or rings situated between the scraper ring and the combustion chamber.
Half-way through this downward stroke, the inertia is again reversed. Immediately the oil previously urged into the deepest part 112 of the recess 109 is projected on to the upper side of the scraper ring, and then, when the inertia overcomes the friction between the ring and cylinder, the ring 106 in turn is thrown on to the lower side of its groove, opening the passage at 108 so that the oil can again flow out to the crankcase as indicated by the arrow fl.
The ring 206 shown in FIG. 2 operates in the same way as that shown in FIG. 1, but its efficiency is increased by the special features described above. Thus, the lip 220, with its sloping surface 221, reduces the tendency of the band of oil to collect in contact with the cylinder, but rather any oil which is collected is directed efficiently into the recess 209. Also, the inclination of the adjacent ring and groove sides 208 accelerates, by means of inertia, the movement of the oil projected on to the upper side of the ring 208 towards the bottom of the groove 203.
During the first part of the upward strokes, the dynamic suction effect due to friction in the gap 215 is accentuated in the chamber 213 by the piston profile at 214, and the suction is transmitted positively to the recess 209. This suction accelerates the passage to the crankcase of the oil scraped off by the lip 220 along the path indicated by the arrow f2.
The rounded portions 211, 223, 224 and 216 further promote the flow of oil indicated by the arrow f2.
During each stroke, therefore, the illustrated pistons recover some or all of the band of oil formed above the scraper ring during the latter part of the upward piston strokes, and then retains the oil in the piston during the downward strokes until the inertia is reversed, when the oil is returned to the crankcase. This is an important contribution to limiting the oil consumption of the engine or other machine.
If the pistons prove too efficient, to the point of interferring with the lubrication of the top of the piston, oil consumption can be adjusted to the optimum level by omitting or modifying certain of the improvements mentioned, for example by providing a curved portion or chamfer instead of the sharp edge on the scraper lip 107 or 207 of the scraper ring or on the collecting lip 110 or 210 on the piston.
While I have disclosed and described preferred kmbodiments of my invention, I wish it understood that I do not intend to be restricted solely thereto, but rather that I intend to include all embodiments which would be apparent for one skilled in the art and which come within the spirit and scope of my invention.
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|U.S. Classification||92/159, 277/436, 277/457, 277/463, 92/160, 277/453|
|International Classification||F16J9/00, F16J1/08, F16J9/20, F16J1/09|
|Cooperative Classification||F16J9/203, F16J9/00, F16J9/206|
|European Classification||F16J9/20B, F16J9/20C, F16J9/00|